Ballast circuits for gas discharge lamps which include an d.c.-to a.c. converter for supplying a.c. current to a resonant load circuit are known. Typically, such circuits include a pair of non-complementary switches in the d.c.-to-a.c. converter. For example, it is common to use a pair of identical, n-channel enhancement mode MOSFETs as the switches. Each of such non-complementary MOSFETs must be controlled by a separate gate-to-source (or control) voltage. This requires level shifting of voltage to couple a single control signal to each of the gate-to-source voltages of the pair of MOSFETs. Such level shifting can be accomplished by a transformer or by conventional bootstrapping means. The transformer method works well at high speeds, but is costly and hard to control. The bootstrapping method, usually implemented by an Integrated Circuit (IC), has good control capability, but is unable to work at high speeds.
It, therefore, is an object of the invention to provide a ballast circuit for a gas discharge lamp that overcomes the foregoing drawbacks.